In vitro cefoperazone proved more active against the tested gram-negative bacteria than either piperacillin or mezlocillin. When administered in 1 g venous bolus the antibiotic achieved high plasmatic concentrations that were still adequate after 8 hours. 33.2% was excreted by the kidneys and a considerable amount by the biliary way. Cefoperazone produced a clinical cure in 35/36 patients (97.22%). A disulfiram-like effect was noted in 18.18%.